The DC-7 was developed by Douglas in response to a 1951 American Airlines request for an airliner to compete with the Lockheed Super Constellation ordered by Trans World Airlines. Powered by a turbo-compound version of the Wright R-3350 engine producing 30% more power than the 18-cyclinder radial R-3350s powering American's DC-6s, the Super Constellation was capable of non-stop transcontinental operations, even into headwinds. Douglas was unenthusiastic about the project, believing it would undermine its DC-6B programme, then in the latter stages of development. However, Douglas was persuaded following American's offer to pay $40m for 25 of the new aircraft, thus covering most of the development costs.
Despite the company's misgivings, the DC-7 sold well, with over 170 delivered to American, Eastern Air Lines, Pan American and United Air Lines. A higher gross weight version was developed, followed by a version capable of non-stop transatlantic operations. Service with major operators was brief with phase-out of the DC-7s beginning less than five years after service entry, as a result of the switch to jetliners. Plans for a version powered by Rolls-Royce Tyne turboprops were abandoned for the same reason.
Many DC-7s went to on enjoy successful careers as freighters, but the complexity and unreliability of the turbo-compound engines has meant survivor numbers have been low for some time. Flying operations have almost certainly now come to a close following the retirement of Erickson Aero Tanker's aerial firefighting fleet in 2020.
First flight: 18 May 53 (c/n 44122, N301AA)
Production: 338, at Santa Monica, CA
First delivery: 10 Oct 53, to American Airlines (c/n 44125, N304AA)
Last delivery: 10 Nov 58, to KLM (c/n 45549, PH-DSR)
Variants: DC-7 - initial production version based on the DC-6B but powered by 4 Wright R-3350-18DA-2 turbo-compound radials, with stretched fuselage and strengthened undercarriage, and seating for up to 99 passengers (105 built);
DC-7B - higher gross weight version with increased fuel capacity, powered by R-3350-18DA-4s (112 built, first flight Oct 54);
DC-7C Seven Seas - long-range version with stretched fuselage, increased wing span, heightened tail fin and further increases to fuel capacity (121 built, first flight 20 Dec 55).
Conversions were made to all-cargo configuration under unofficial designations DC-7F, DC-7BF and DC-7CF. An additional 3 DC-7Cs were converted in 1966 by UTA Industries to AMOR (avions de mesures et d'observations au réceptacle) for satellite launch and re-entry tracking by the Centre d'Essais en Vol.